This invention relates to an alignment jig used to place and align a cutting guide in order to make a transverse cut on the tibia and/or femur.
Intramedullary instruments are used by surgeons to place and subsequently align a cutting guide on a tibia or femur to a specific flexion-extension and varus-valgus angle with respect to the mechanical axis of the tibia or femur. Once the cutting guide is aligned to the desired settings, it is pinned to the bone for stability and used to guide a saw blade to make a transverse cut on the bone as required in total knee replacement surgery. The transverse cut would be on the proximal tibia or distal femur.
A drawback of some of these instruments is that once varus-valgus and flexion-extension adjustments are made and locked in place, this alignment setting can slip during the subsequent pinning of the cutting guide to the proximal tibia.
Typically, the alignment settings are locked by tightening a thumbscrew. The holding power of the screw is proportional to the amount of torque that is applied to the thread by the surgeon. Slippage may occur because the amount of torque that can be applied by hand to a knob of limited size, and with slippery gloves is somewhat limited. Additionally, if the jig remains in place during the cutting operation, as is usual in revision surgery, the vibration caused by the saw may loosen the screws.
As used herein, when referring to bones or other parts of the body, the term “proximal” means closer to the heart and the term “distal” means more distant from the heart. The term “inferior” means toward the feet and the term “superior” means towards the head. The term “anterior” means towards the front part of the body or the face and the term “posterior” means towards the back of the body. The term “medial” means toward the midline of the body and the term “lateral” means away from the midline of the body.